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Microwave Sintering of Ceramics for Dentistry: Part 2

R Vaderhobli*,S Saha

Fourteen dental copings (zirconia stabilized with 3 mol% yttria) were layered with Noritake dental glass-ceramic and sintered in the microwave furnace with various sintering temperatures. Sintered zirconia rectangular beams measuring 50 mm in length, 4 mm in width and 0.75 mm in height were coated with the dental glass-ceramic and sintered in the microwave furnace. These were subjected to a four-point bend test to calculate modulus of rupture. Sintering temperature of 800°C in the microwave furnace with ramp rates in excess of 100°C per minute was sufficient to attain good sintered crowns. Indentation hardness with 200g loads and 500g loads for the microwave-sintered teeth resulted in hardness values of 0.685 ± 0.0245 GPa and 6.56 ± 0.4 GPa. The indentation fracture toughness values with 200g and 500g were calculated to be 2.26 ± 0.8 MPa(m)0.5 and 0.97 ± 0.1 MPa(m)0.5 respectively and agreed well with the published values [1]. The failure load for the layered beams in the bend test was 81.8 ± 17.7 N and the resulting modulus of rupture was 632 ± 105 MPa.